looking for some brains to pick about mafs

[txoutlaw]

ok, here we go!

has anyone ever thought about or tried to use a maf from another vehicle on an FI car? what i'm getting at is we are generally stuck with SD tunes on FI cars! i know that there are mafs that do not peg out on FI cars of other makes. in my ealier tuning days with fords (no flames please!) we had a wide choice of mafs. some better at be sucked through, others better at being blown through. the point being that there has to be an answer to not having to do SD only tunes for these cars that are FI.

so lets do some looking and talking on the subject! a few HUNDRED heads have got to be better than ONE!!!!!!!!!

[Bill@HPTuners]

someone correct me if im wrong but its not the maf that is the problem I believe the pcm is hardcoded to a limit of 512 g/sec which when met your off the maf table. A custom OS might be able to fix that problem but im not a software designer just a user so that would have to be answered by the guys at hpt if its even possible.

[S2H]

once you run out of Air at 512 g/sec.....you will be stuck using SD as it will be the only way around that

[jimmyblue]

So does the Dynamic Airflow allow more
than 511 g/sec, and just the MAF table
function / quantity is gimp?

I smell a minor OS fiddling opportunity.
Though maybe it isn't so minor.

Anybody running a big-balls speed density
3-bar tune and logging DynAir over 511g/sec?

[txoutlaw]

ok, so lets prod ken, keith or chris to help us out!

heres a thought, the Pontiac GTP cars use basicaly the same system, however they are superchared as well as the SS cobalt. so would it be possible to use some of the OS systems from those cars in the LSx programming?

some people that have or want their cars to be FI and tuned while still using the maf due to personal or legal reasons!

it just seems to me that this would be possible, however i'm not the creator or owner of HPT, nor am i a computer programmer.

[txoutlaw]

jimmyblue, i read your reply to this question on LS1TECH

ok, so lets say you stick what weve got! so if i understand you correctly, you can set PE map enable, and PE tps (hot and Cold) enable at a point that begins just before you reach boost. so in doing that you can enter PE in order to tune an FI car? in doing so i am assuming that you can tune an FI car making up to 800 HP (given that all things needed to support this HP level are there, fuel pump, inj., and so on)!

i know i've seen somone tune one that made 897 crank HP without an SD only tune, is this how? if i'm missing something SOMEONE OR ANYBODY PLEASE jump in and let me know!!!!!!

[Chris@HPTuners]

the thing is you can tune anything for WOT and constant boost. it really doesn't matter if you have a MAF or SD, 1bar or 3bar assuming your injectors are large enough you can just richen the PE table until the fueling is ok.

This is not the right way to do it, but if your car runs at idle and WOT only then almost any method works.

If you go and buy/make a MAF that reports a lower frequency for a higher airflow then you give yourself some headroom, but as others have said the upper limit is the 512 g/sec airflow. This could be changed (with a moderate amount of work) but is not something we are looking at currently.

BTW, there are cars out there making 1000+ RWHP on the stock PCM.

Chris...

[jimmyblue]

Almost seems like, if you were up for the broad
fiddling required, you'd rather run a 2-bar MAP
(with its output uncalibrated), and an extremely
ported or custom calibrated MAF (such that it
read 12kHz at 256g/sec) and just pretend all
airflows / cylinder air are half of actual. Guess for
the fuel side you'd use boost referenced regulator
so the pressure relation there is a don't-care,
table-wise, flatline it.

Since you're not going to be putting a 4L60E
behind a motor like that, all you care about is
fuel and spark, seems like it would just be a
really extensive data remapping. And you could
build the bottom half of the new tables by
using every other row or column, squoze down?

[Chris@HPTuners]

the most common way to do this is halve the MAF freq output and then halve your injector flow rates as well, so the PCM puts in twice as much fuel for the "tricked" half airflow.

You could run two mafs in parallel and just read one etc. etc. I think Harlan did this on his car, except he used a black box that actually averaged the two MAF signals before sending to the PCM. Then simply halve the injector flow rates.

[S2H]

the most common way to do this is halve the MAF freq output and then halve your injector flow rates as well, so the PCM puts in twice as much fuel for the "tricked" half airflow.

You could run two mafs in parallel and just read one etc. etc. I think Harlan did this on his car, except he used a black box that actually averaged the two MAF signals before sending to the PCM. Then simply halve the injector flow rates.

so whats the magical way to get the output of the MAF to be half???
as this would come in very beneficial in many applications...

[Casey]

so whats the magical way to get the output of the MAF to be half???
as this would come in very beneficial in many applications...

Table values /2

[S2H]

Table values /2

I was asking about getting the MAF to report less HZ as people do max that out too

[Chris@HPTuners]

so whats the magical way to get the output of the MAF to be half???
as this would come in very beneficial in many applications...

no idea, i never pulled a MAF apart and had a look at whats in there. It's real easy for the Fords since the MAF outputs a simple 0-5V but GM uses a frequency signal, just some kind of frequency translator like those MAF-T things many people use.

[txoutlaw]

no idea, i never pulled a MAF apart and had a look at whats in there. It's real easy for the Fords since the MAF outputs a simple 0-5V but GM uses a frequency signal, just some kind of frequency translator like those MAF-T things many people use.

ok,
so where to buy or how do you build a maf-t?

[Chris@HPTuners]

try google for "MAF Translator"

The V6 guys use them a lot, not sure where you buy them, maybe Scott over at Intense Racing can give you some help.

[jimmyblue]

Since the MAF output wants to be halved, and the output
signal swings 0-5V, all you would need is an old 74HC74
flip-flop set up to toggle (D=Qb). There's your straight
divide-by-two. I don't believe the PCM cares about the
pulse width for its frequency reading.

Now, behind the PCM internal limit lies the MAF's upper
frequency internal limit. This is unknown (to me). Once
you see the MAF pulse train get to about 75% high duty
cycle I'd start to worry. I measured the pulse widths once
with a 'scope but don't recall now what that was. Anyway
figure absolutely no way to get past a frequency of 1/PW,
nohow.

Good news is, the MAF response (freq/airflow) is compressive,
appears like logarithmic to me. So 2X the indicated airflow is
not 2X the frequency.

Other way to go is, as I mentioned, extreme porting. Like
get yourself a good ol' LS1 MAF and a 2000CFM blower,
put your descreened truck MAF in tandem-tube, and get
two frequency readings (pair of $39 DMMs, if you pick
the right ones). Hog, hog, hog it out with a periodic read
until you get the frequency for 256g/sec out of the victim
(9600Hz) when the stocker is right at 12kHz. There you be.
This way does not challenge the MAF built-in electronics
at all, it's a pure physical recalibration. Questionable in the
middle ground, I suppose, but given the circumstances that's
probably among the least of your problems, and soluble.

[tici]

the most common way to do this is halve the MAF freq output and then halve your injector flow rates as well, so the PCM puts in twice as much fuel for the "tricked" half airflow.

You could run two mafs in parallel and just read one etc. etc. I think Harlan did this on his car, except he used a black box that actually averaged the two MAF signals before sending to the PCM. Then simply halve the injector flow rates.

As I answered the same on another forum "someone" wrote:
"by the way that a pretty elaborate scheme youve come up with!!!!!!"

hehe!

If the double MAF assembly is well designed each MAF will see tha same amout of air. Actually you need only one functioning MAF... no black box, no oscilloscope.

Also another idea: change the resistors in the MAF so that they will show another value for the same amount of air. But that could be complicated.